This disclosure is directed to a valve structure to be used at relatively high pressures. The pilot valve of this disclosure is installed with and connected to a safety relief valve. It operates the safety relief valve. The safety relief valve is one which is adapted to releasably blow down a very high pressure source. For instance, the device can be used with inlet pressures of perhaps 6,000 psi or so. As the inlet pressure to the safety relief valve rises, the pressure approaches the level for the pilot valve to trip it. The pilot valve of this invention is particularly adapted to respond to this inlet pressure. It controls pressure in an outlet line which is connected to the safety relief valve. The safety relief valve is thus operated in the required manner to thereby open the safety relief valve. This control pressure opens the safety relief valve when it exceeds the preset pressure and holds it open until the inlet pressure returns to the preset level.
It is important to know the operative state of the pilot valve. The operative state is determined by several factors. While a few of them are scale factors that are intrinsically built into a given device, it is just as important to note that the factors controlling operation of the pilot valve create a need for the pilot valve to track a moving target, so to speak. It will be appreciated that the device is used over a wide range of relatively high pressures. For instance, it can be installed to monitor pressures in the range of 1,500 to 6,000 psi. Consider, as an example, operation of the pilot valve at inlet levels of this sort. The device is able to track inlet pressures up to the set level within the specified range. The outlet pressure also tracks with the inlet pressure. In other words, once a selected inlet pressure has been determined, the outlet pressure is a percentage of this pressure as reflected by the pressure levels in the outlet line. The outlet line is delivered to the safety relief valve, and provides a fluid signal for operation of the pressure relief valve. This can be accomplished even though the fluid of interest flowing through the safety relief valve is a gas or liquid.
The device of this disclosure optionally includes an indicated output signal at a plunger to verify the operative state of the valve. If the valve is open to exhaust fluid to the exhaust port, thereby dropping the outlet line pressure, this pressure pulse signal is applied to the safety relief valve to trigger operation of that valve.
Many objects and advantages of the present invention are provided in the fashion to be described hereinbelow. This pilot valve is particularly adapted to be used with a safety relief valve of the sort disclosed in application Ser. No. 290,252 which was filed on the common filing date of this disclosure and by the common inventor. That disclosure is hereby incorporated by reference into the present disclosure. Such a valve is also shown at page 4 of Catalog 1531 of Anderson, Greenwood & Co., 1980.